Rhodium and ruthenium compositions

ABSTRACT

Compositions having the general formula R2TX are disclosed where R is taken from the group consisting of Rh and Ru; where T is taken from the group consisting of Fe, Co, Ni, V, Cr and Cu; and where X is taken from the group consisting of Al, Ga, In, Tl, Ge, Sn and Sb. Compositions wherein T is taken from the group consisting of Fe, Ni and Co and where X is taken from the group consisting of Ge and Sn are particularly useful as ferromagnetic materials. Examples of such compositions are Rh2FeGe and Ru2FeSn.

Elnited States Patent [1 1 Suits Sept. 9, 1975 RHODIUM AND RUTHENIUM CGMPOSITIONS [52] US. Cl 75/172 R [51] Int. Cl. C22C 5/04 [58] Field of Search 75/172 R, 134 N, 134 B,

[56] References Cited UNITED STATES PATENTS 7/1964 Walter ..75/122 7/1964 Walter 8/1964 Bither 75/122 8/1964 Walter 75/122 [5 7] ABSTRACT Compositions having the general formula R TX are disclosed where R is taken from the group consisting of Rh and Ru; where T is taken from the group consisting of Fe, Co, Ni, V, Cr and Cu; and where X is taken from the group consisting of Al, Ga, In, Tl, Ge, Sn and Sb. Compositions wherein T is taken from the group consisting of Fe, Ni and Co and where X is taken from the group consisting of Ge and Sn are particularly useful as ferromagnetic materials. Examples of such compositions are Rh FeGe and Ru FeSn.

10 Claims, N0 Drawings RHODIUM AND RUTHENIUM COMPOSITIONS BACKGROUND OF THE INVENTION 1. Fieldof the Invention This invention relates to new compositions and more particularly to rhodium and ruthenium compositions.

2. Description of the Prior Art Ferromagnetic materials are broadly old and many such compositions are known. Many of these ferromagnetic compositions have one or more inferior properties. For example, many of these compositions do not have a sufficiently high Curie temperature, a high enough saturation magnetization value or are not sufficiently resistant to corrosion.

Ferromagnetic materials used in inductive magnetic recording devices generally have a relatively high Curie temperature of 200C or higher. The Curie temperature of the materials used in beam addressable recording devices generally is between 100C and 200C. It is understood that the Curie temperature required for any given application is interdependent upon other material parameters as well as the device design.

Compositions having the general formula R MnX and RMnX where R is Pt, Rh, Ir, Ru, or Os and X is Al, Ga, Ge, In, Sb, Si or Sn are described in the Journal of Applied Physics, 42 1336, 7 (1971). Some of these manganese compositions exhibit ferromagnetic properties.

Ferromagnetic compositions containing Rh and Fe and a third element from the group IIlA, IVA or VA of the Periodic Table are discussed in the US. patent to Bither, U.S.'Pat. No. 3,144,324. The compositions disclosed in the Bither patent have the general formula Fe Rb,,X,. where u and b are between 0.8 and 1.2. None of these prior art ferromagnetic compositions are presently being used to any significant extent.

SUMMARY OF THE INVENTION It is a primary object of this invention to provide a new class of compounds.

It is another object of this invention to provide a new class of ferromagnetic compositions.

It is still another object of this invention to provide a group of compounds having a new structure.

It is yet another object of this invention to provide ferromagnetic compositions having a high magnetization value, corrosion resistant properties and a Curie temperature greater than 100C.

These and other objects of this invention are accomplished by a composition having the general formula R TX where R is taken from the group consisting of Rh and Ru; where T is taken from the group consisting of Fe, Co, Ni, V, Cr and Cu; and where X is taken from the group consisting of Al, Ga, In, Tl, Ge, Sn and Sb. Compositions particularly useful as a ferromagnetic material include those where T is taken from the group consisting of Fe, Co and Ni and where X is taken from the group consisting of Ge and Sn. A number of these compounds have a novel tetragonal structure.

DETAILED DESCRIPTION OF THE INVENTION This invention describes compositions defined by the general formula R TX where R is taken from the group of Rh or Ru; T is taken from the group consisting of Fe, Co, V, Cr, Cu and Ni; and X is taken from the group consisting of Al, Ga, In, Tl, Ge, Sn and Sb.

All of these compositions are useful as corrosion resistant materials. They are also useful to some extent as electrical conductors.

The compositions having T taken from the group of Fe, Co and Ni and having X taken from the group of Ge and Sn are particularly useful as ferromagnetic materials. One of these compositions, Rh FeGe, has a Curie Temperature of 353C. The Curie temperature of some of the compositions covered by this invention are set forth in the following table.

Composition Curie Temperature, C

Rh FeSn 3 l0 Ru FeSn 300 Ru FeGe 200 'Rh CoSn l 7 l Rh NiSn 25 The magnetism of these ferromagnetic compositions varies depending upon the particular combination of metals used in the above general formula. Magnetiza tion values of the order of 30 to 50 emu/gm have been obtained with certain combinations.

This group of compounds has one of two structures. One structure is the well known Heusler structure L2 which has a cubic lattice. The other structure has not been described in the literature before. It is a tetragonal lattice with atomic positions on this lattice as in the Heusler L2 structure. This new structure will be arbitrarily referred to as the D structure in this application.

Specifically, the D structure is given by space group P4 /ncm (origin at center 2/m) with R atoms at 4e (Z 1/4) and 4b, Tatoms at 411, and X atoms at 40. This notation is that used in the International Tables for Xray Crystallography, Vol. 1, Kanoch Press 1952. The departure from the cubic lattice is large for the D structure. Typically, for the D structure the c lattice shows an elongation of 20% relative tothe a axis.

The fact that the chemical composition of some of the compounds yields a new structure is of considerable significance. It is well known that identical chemical compositions, for example, graphite and diamond, which have different structures, have very different physical properties.

It has been observed that the Ru compositions of this invention have a L2 structure. The Rh compositions may have either a D or an L2 structure depending upon the T and X constituents.

While the general formula R TX shows specific stoichiometric amounts, this invention includes variations from those specific stoichiometric amounts. The stoichiometric amounts may be varied for one or more of the constituents separately or in combination to obtain the desired properties. The stoichiometric amount variance is limited by the requirement of maintaining the appropriate cubic or tetragonal structure, i.c., if you add too much or too little of one of the constituents you no longer have the cubic or tetragonal structure.

The compositions described herein are prepared by mixing together the elemental powders in stoichiometric amounts, sealing the resulting mixture in the evacuated quartz ampoule, and then annealing the ampoule at elevated temperature in order to chemically react the powder to form the compound.

EXAMPLE 1 Elemental powders of rhodium, iron and tin in the atomic ratio Rh Fesn were mixed together and vacuum annealed at 250C for 7 hours. It was then further annealed at 700C for 6 days. The mixture was quenched by placing the ampoule in water. This product had the following properties:

1. Structure: D

2. Lattice constants: a 5.87A, c 6.92A

3. Curie temperature: 310C 4. Magnetization (20C, 20kOe): 45 emu/gm Another sample of Rh FeSn was pressed and are melted into an ingot. This ingot was mechanically polished to provide a mirror surface. The mirror surface was then exposured for 24 hours in an atmosphere containing S N0 0 H 5, C1 and having 80% relative humidityyThe conditions were designed to simulate a typical urban industrial environment. The polished surface showed no evidence of atmospheric corrosion. A reference sample of FeCo in the same test showed severe corrosion.

EXAMPLE 2 Elemental powders of rhodium, cobalt, and tin in the atomicratio were mixed together, annealed at 250C for 7 hours and at 700C for 7 days. Then' it was water quenched. This sample had the following properties:

1. Structure: D

2. Lattice constants: a 5.83A, c 6.9 1A

3. Curie temperature: l7lC 4. Magnetization (C, 20kOe) emu/gm EXAMPLE 3 Elemental powders of rhodium, iron and germanium in the atomicratio were mixed together and annealed at 250C for 6 hours and at 700C for 3 days. It was quenched and then ground in a morter and pestle to a fine powder. This powder wasvacuum annealed again at 800C for 4 days and furnace cooled. This sample had the following properties:

1. Structure: D

2. Lattice constants: a 5.68A, c 6.66A

3. Curie temperature: 353C 4. Magnetization (20C, 20kOe); 49 emu/gm EXAMPLE 4 Elemental powders of ruthenium, iron and germanium in the atomic proportion:

Ru FeGe were mixed together and annealed at 250C for 6 hours and at 800C for 5 days. It was then furnace cooled.

This sample had the following properties:

1. Structure: L2 2. Lattice constant: a 5.948A 3. Curie temperature: 200C 4. Magnetization (20C, 20kOe): 38 emu/gm EXAMPLE 5 Elemental powders of ruthenium, iron and tin in the atomic proportion Ru- FeSn were mixed together and annealed at 250C for 6 hours and at 700C for 7 days. It was then water quenched. This sample had the following properties:

1. Structure: L2

2. Lattice constant: a 6.19A

3. Curie temperature: 300C 4. Magnetization (20C, ZOkOe): 48 emu/gm What is claimed is:

l. A composition having the general formula where R is taken from the group consisting of Rh and Ru; where T is taken from the group consisting of Fe, Co, Ni, V, Cr and Cu; and where X is taken from the group consisting of Al, Ga, In, Tl, Ge, Sn, and Sb.

2. A composition as described in claim 1 wherein the structure is tetragonal.

3. A composition as described in claim 1 wherein T is taken from the group consisting of Fe, Co and Ni.

4. A composition as described in claim 1 wherein X is taken from the group consisting of Ge and Sn.

5. A ferromagnetic composition having the general formula where R is taken from the group consisting of Rh and Ru; where T is taken from the group consisting of Fe, Co and Ni; and X is taken from the group consisting of Ge and Sn.

6. A ferromagnetic composition as described in claim 5 having the formula Rh FeGe.

7. A ferromagnetic composition as described in claim 5 having the formula Ru FeGe.

8. A ferromagnetic composition as described in claim 5 having the formula Rh FeSn.

9. A ferromagnetic composition as described in claim 5 having the formula Ru FeSn.

10. A ferromagnetic composition as described in claim 5 having the formula Rh CoSn. 

1. A COMPOSITION HAVING THE GENERAL FORMULA
 2. A composition as described in claim 1 wherein the structure is tetragonal.
 3. A composition as described in claim 1 wherein T is taken from the group consisting of Fe, Co and Ni.
 4. A composition as described in claim 1 wherein X is taken from the group consisting of Ge and Sn.
 5. A ferromagnetic composition having the general formula R2TX where R is taken from the group consisting of Rh and Ru; where T is taken from the group consisting of Fe, Co and Ni; and X is taken from the group consisting of Ge and Sn.
 6. A ferromagnetic composition as described in claim 5 having the formula Rh2FeGe.
 7. A ferromagnetic composition as described in claim 5 having the formula Ru2FeGe.
 8. A ferromagnetic composition as described in claim 5 having the formula Rh2FeSn.
 9. A ferromagnetic composition as described in claim 5 having the formula Ru2FeSn.
 10. A ferromagnetic composition as described in claim 5 having the formula Rh2CoSn. 